Electric automobiles have long been an item of novelty and an object of curious inquiry to the everyday commuter. However, it appears with the earth's depleting supply of petroleum fuel and society's ever increasing awareness of the degenerative effect of the pollutants emitted in the exhaust of an automobile powered by a petroleum based fuel upon the environment, electric automobiles have recently become the object of intense research and development in an effort to produce a economically viable mass production electric automobile. The recently heightened interest in electric automobiles is due in large part to the zero emission vehicle laws recently passed in several states, including California, which have set minimum electrical car sales figures per year in those states for the car manufacturers to meet based upon a percentage of their total yearly sales in that state. Most of these laws are to take effect in 1998 or soon thereafter. In the race to produce such an electric automobile, the weakest link to date has been the absence of a rechargeable power source, i.e. battery, capable of producing the specific power (watts per pound) required to achieve an adequate cruising speed and the specific energy (watt hours per pound) required for a minimum 200 mile travel range. In addition, to be commercial viable, the power source must meet two other requirements, specific cost and safety of operation. Specific cost is merely an expression of the battery cost per pound which is an indicator of the cost of owning and operating the battery.
To better understand the operating requirements on a battery used to power an electric automobile, a general model for specific cruising power and specific cruising energy per mile has been developed to project the specific power and specific energy typically needed to produce a minimum 200 mile range in an electric road vehicle.
For the general model, six speed ranges are used, five of which cover a certain type of road use and a fifth which covers non-useful road operations such as heavy construction equipment. The lower speed range, less than 25 mph, is used to define the lowest limit for the specific energy and power requirements. These speed ranges, designated M, S, H, C, E, and F, am shown below along with a brief description of their operation.
______________________________________ WORLD VEHICLE MARKET OPERATION PERFORMANCE RANGES: DESCRIPTION: ______________________________________ (M) Material handling under 25 mph no useful road operation (S) Secondary road 25-45 mph low speed road operation (H) Highway 45-55 mph general highway travel (C) City expressway 55-65 mph urban expressway travel (E) Expressway 65-75 mph expressway travel (F) Fast expressway over 75 mph long distance expressway travel ______________________________________
Next, road vehicles are divided into four design groups designated N, A, U, and T. The main characteristics of each group are identified and listed below in order of increasing ratios of power system weight to total weight. The greater ratios of power system weight to total weight will result in less specific power and specific energy requirements from a battery at the expense of passenger and cargo space.